Hydrofining naphthenic lubricating oil



Feb. 7, 1956 J. R. MILLER ETAL 2,734,019

HYDROFINING NAPHTHENIC LUBRICATING OIL Filed April 22, 1953 Furnace HeaierW/g;

Feed (Naphihenic Lubricating Oil) 1 5 Burners I9 33 4 Q L. 20 Cobalt Molybda'e "on Alumina Catalys' 32p. Reacnon Zone.

0 Gas 35 37 25. 23 Water 24 NGPMM Separator vacuum [27 26 Sirippcr 28 '29 Sream 38 --Produci INVENTORS.

James R. Miller, BY Edward F. Wad/ey,

mag

v ATTORNEY.

United States Patent HYDROFININGNAPHTHENIC LUBRICATING OIL James R. Miller and Edward F. Wadley, Baytown, Tex., assignors, by mesne assignments, to Esso Research and Engineering Company, Elizabeth, N. 3., a corporation ofDelaware Application April 22, 1953, Serial No. 350,437

6 Claims. (Cl. 196-24) The present invention is directed to a method for.

treating lubricating oil fractions. More particularly, the invention is directed to a method for producing low cold test lubricating oils. In its more specific aspects, the invention is directed to the treatment with hydrogen at an elevated temperature of :a naphthenic lubricating oil fraction.

The present invention may be briefly described as a method for treating a naphthenic lubricating oil fraction containing undesirable aromatic hydrocarbons, sulfur, naphthenic acids and nitrogen. The naphthenic lubricating oil fraction is contacted at an elevated temperature with a cobalt molybdate on silica-free alumina catalyst in the presence of hydrogen under conditions such that at least a portion of the aromatic hydrocarbons are converted and the sulfur, naphthenic acids and nitrogen content of the lubricating oil fraction is substantially reduced.

The feed stock to the present invention is a naphthenic lubricating oil fraction which contains aromatic hydrocarbons. The lubricating oil fraction contains sulfur, naphthenic acids and nitrogen in a small amount which may be combined with the aromatic hydrocarbons in the form of compounds having'a heterocyclic ring. However, some of the nitrogen, sulfur and oxygen may be present in the form of simple side chains on the aromatic nucleus.

The naphthenic lubricating oil fractions preferably are obtained from the Coastal fields in Texas and Louisiana. However, naphthenic lubricating oil fractions containing aromatic hydrocarbons, sulfur, naphthenic acids and nitrogen may be obtained from other sources and are amenable to treatment in accordance with the present invention to form improved lubricating oils.

The temperature at which the lubricating oil fraction is contacted with the catalyst is in the range from 650 to 750 F. with a preferred range of about 675 to 725 F.

Pressures may range from 500 to 800 pounds per square inch gauge and preferably will be in the range from about 725 to 775 pounds per square inch gauge.

The amount of hydrogen employed may vary with the viscosity of the oil being treated and suitably may range from 200 to 2000 standard cubic feet of hydrogen per barrel of lubricating oil fraction treated. A suitable amount is in the range from about 200 to about 1600 standard cubic feet of hydrogen per barrel. Although this amount of hydrogen is specified, actually a feature of our invention is the low consumption of hydrogen. Thus the amount of hydrogen actually consumed in the reaction may vary from about 50 to about 400 standard cubic feet of hydrogen per barrel of feed depending on the amount of hydrogen employed initially and the conditions of the treatment. The reason that more hydrogen is actually required than is consumed is not known at present.

' The lubricating oil'fraction should suitably contact the catalyst at a liquid space velocity in the range from 0.25

ice

to 6 volumes of lubricating oil fraction per volume of catalyst per hour. Again the liquid space velocity will vary depending on the viscosity of the lubricating 'oil fraction charged and the other conditions employed.

Under the foregoing conditions, at least a portion of the aromatic hydrocarbons are converted and the content of the naphthenic acids, nitrogen and sulfur is substantially reduced. It is to be emphasized, however, that the treatment in accordance with our invention is not a desulfurization operation and it is advantageous that the oil have a residual sulfur content which contributes, in a manner unexplainable at present, to the desirable quality of our product.

The catalyst employed in our invention is a cobalt molybdate on alumina catalyst. The cobalt molybdate may suitably be present in the catalyst in an amount in the range from about 5% to 25% by weight while the alumina willsuitably be present in an amount in the range between 95% and by weight. A preferred catalyst composition is 15% by weight of cobalt molybdate and by Weight of alumina.

The alumina employed in our invention is a silicafree alumina. In other words, it is specifically contemplated that the catalyst should be substantially free of silica. A catalyst may be prepared by depositing. onv or impregnating a silica-free alumina with cobaltmolybdate. For example, silica-free alumina may be obtained by preparing gamma alumina from the hydrate, boehmit'e. Also a silica-free alumina-cobalt molybdate catalyst 'may be prepared by treating 'a silica-free aluminagel by heating the gel over 'a period of about 16 hours at 1000" F. After the heating the gel is cooled at substantially room temperature andthen is admixed thoroughly with ammonium molybdate and cobalt acetate with just enough water to form a paste. of the mixture. Thepaste is then dried at 250 F. for 12 hours. The dried catalyst is thenpilled and activated by-heatingfor a period of 12 hours at 1000 F.-1500 F. Other methods may be suitably used for preparing the cobalt molybdate-silica-free catalyst.

The invention will be further'illustrated by'referen'ce to the drawing in which thesingle figure is a flow diagram of. a preferred mode of conducting the invention.

Referringnow to the drawing, numeral 1 1 designates a charge line by which a feed hydrocarbon is introduced into the system. The feed hydrocarbon may suitably be a naphthenic lubricating oil'fraction'which' is introduced from a source not shown. The lubricating oil fraction in line 11 is pumpe'dzby way of'pum l'z into-a suitable heater or furnace 13 provided withhea-ting coils 14 and burners 15 which serve to raise the temperature to a temperature in the range given, for example, approximately 700 F. The heated lubricating oil' fraction then issues from heater 13' by way of line 16 and has admixed with it hydrogen introduced by line 17 controlled by valve-1 8 at a temperature of approximately 450 F. This hydrogen admixes with the oil and the admixture is then introduced by'line 16 into a reaction zone 19 provided With'a bed 20 of cobalt molybdate on alumina catalyst which may be suitably arranged on a grid plate 21. The hydrogen-lubricating oil mixture passes down through bed 20 at a space velocity in a range from about .25 to about 6 volumes of feed per volume of catalyst per hour and under conditions obtaining there is a conversion of aromatic hydrocarbons and the sulfur, nitrogen a'nd oxygen compounds contained in the lubricating oil.

The product issues from reaction zone 19 by way of line 22 controlled by valve 23 and is introduced thereby into a separation zone 24 wherein a separation is made between the gas' and the liquid product, the gas being withdrawn from the system by way of line 25. The product is withdrawn from separator 24 by line 26 which introduces it into a vacuum stripping zone 27 which may, if desired, be provided with suitable vapor-liquid contacting means not shown. In vacuum stripper 27 provision is made to introduce stripping steam into a lower portion of the stripper 27. To this end, line 23 and jets 29 are provided for introduction of stripping steam to remove gases and volatilizable material from the treated product. It is desirable to operate the stripping zone 27 under a subatmospheric pressure of about 1 inch mercury in order to remove the volatilizable material without subjecting the product to a high temperature. To this end, stripper 27 is provided with an overhead line 30 through which the non-condensible gases and volatilizable material are removed into a separating vessel 31. This vessel is provided with line 32 for removal of the light products and a vacuum jet or other suitable device 33 for reducing the pressure on the vessel 31 and stripper 27. The light gases are drawn off from the vessel 31 by line 34. Vessel 31 is provided with a leg 35 for accumulation and drawotf of water resulting from the condensation of the stripping steam. This water is withdrawn from leg 35 by line 36. Volatilizable compounds, such as naphtha, formed during the reaction may be withdrawn from vessel 31 by line 37 for further use as may be desired.

The product, which is the finished lubricating oil, is withdrawn from stripper 2'7 by line 38 and may be suitably used as a lubricating oil of a desired and improved quality.

By employing the foregoing described process, it is possible to produce a low cold test lubricating oil having improved color properties and also improved stability. In fact, the color of the lubricating oil produced in accordance with our invention is resistant to oxidation and does not tend to deteriorate on storage.

In order to illustrate further the beneficial results of our invention, a number of distillate lubricating oil fractions from a Texas Coastal crude was treated with hydrogen at an elevated temperature under conditions such as have been outlined before. The results of these runs ing oil fraction are presented in Table I.

drogen causes conversion of only the aromatic hydrocarbons and the compounds containing sulfur, nitrogen and oxygen, the paratfins and naphthenes being substantially unconverted. This reduction in the aromatic content and the reduction in sulfur, nitrogen and oxygen results in an improved lubricating oil.

In order to illustrate the invention further a number of runs were made on a Coastal lubricating oil fraction in which the temperature and space velocity were varied. In these operations, a 15% cobalt molybdate on silicafree aiumina was used as the catalyst. Pressures were approximately 750 pounds per square inch gauge and from 500 to 2000 standard cubic feet of hydrogen per barrel of feed stock were employed. The results of these runs are presented in Table II.

Table 11 Run No 1 2 3 4 5 750 700 700 700 Color, '1. R 11% 12% 15% +17+ +17+ Sulfur Wt. Percent. 0. 09 0.11 0. 09 0. 12 0.06 Via/100, SSU 671 750 675 781 619 Yield, Vol. Percent 97. 0 98. 7 98. 5 99. 5 96. 6

It will be noted from the results in Table II that the space velocity varied from 0.25 to 2 with best results being obtained at the lower space velocities. It is noteworthy that the sulfur content is approximately 0.10 in all of the runs.

While these runs show that products are produced having better than 11 /2 Tag-Robinson color, it is specifically contemplated that We may produce products having a lower Tag-Robinson color. In fact, a Tag-Robinson color as low as 7 is considered quite desirable and We contemplate that a finished lubricating oil fraction may be produced in accordance with our invention having such a color. Further, the color obtained under a given set of operating conditions varies as the viscosity of the lubricating oil distillate being charged varies. For example, with an SSU at F. distillate, we may obtain an 18 Tag-Robinson color whereas a 100 SSU at 210 F. dis

Table l Aromatics+Sulfut,

Nitogen. and (P Sugf i'n Wt (P Nitpogenwt g g fi gi. xygen ercen y ercen y Distillate (Percent by Vol.) samp 16) Charge Product Charge Product Charge Product Charge Product 80 SSU at 100 F. Coastal Dlstil- 35 32 O. 21 0. 11 0. 02 0. 02 1. 390 O. 000 250 SSU at 100 F Coastal Distilla 37 34 0. 23 0. ll. 0. 02 0. 01 l. 540 0. 002 1,000 SSU at 100 1 Coastal D late 40 35 0. 26 0. 11 0. 04 0. O2 1. 65 0. 000 100 SSU at 210 F. Coastal Distillate 42 37 0. 27 0. 15 0. 05 0. 03 1. 86 0. 002

It will be clear from an examination of the data in Table I that our invention reduces the aromatic content, sulfur, nitrogen and neutralization number of the several Coastal distillates which were treated in accordance with our invention. It will be noted in every case that the sulfur content was approximately 0.l0%, actually varying between 0.11 and 0.15. It is advantageous to have a residual sulfur content of 0.10% to confer product quality on the lubricating oil fraction obtained by the treating operation.

It will also be noted that the naphthenic acid content as represented by the neutralization number has been reduced substantially to zero and that the nitrogen content has also been reduced.

Of particular further interest is the aromatics plus sulfur, nitrogen and oxygen content which has been reduced in every case from 3 to 5%. In our operations, the bytillate may yield a 9 Tag-Robinson color when processed under the same conditions.

The product produced in accordance with our invention is suitable for use as an improved lubricating oil and on employment in an engine performs satisfactorily.

The nature and obiects of the present invention having been completely described and illustrated, what we wish to claim as new and useful and to secure by Letters Patent is:

l. A method for treating a naphthenic lubricating oil fraction containing aromatic hydrocarbons and sulfur, naphthenic acids, and nitrogen which comprises contacting said fraction with a cobalt molybdate on silica-free alumina catalyst. at a temperature in the range from 650 to 750 F, at a pressure in the range from 500 to 800 pounds per square inch gauge in the presence of hydrogen in an amount in the range from 200 to 2000 standard cubic feet per barrel of said fraction with a hydrogen consumption in the range from about 50 to about 400 standard cubic feet per barrel of said fraction, and at a liquid space velocity in the range from 0.25 to 6.0 volumes of said fraction per volume of catalyst per hour such that only portion of said aromatic hydrocarbons is converted and the sulfur, naphthenic acids, and nitrogen content of said fraction is substantially reduced, the paraflins and naphthenes in said fraction being substantially unconverted.

2. A method for treating a naphthenic lubricating oil fraction containing aromatic hydrocarbons and sulfur, napht'nenic acids, and nitrogen which comprises contacting said fraction with a cobalt molybdate on silica-free alumina catalyst at a temperature in the range from 650 to 750 F., at a pressure in the range from 500 to 800 pounds per square inch gauge in the presence of hydrogen in an amount in the range from 200 to 2000 standard cubic feet per barrel of said fraction with a hydrogen consumption in the range from about 50 to about 400 standard cubic feet per barrel of said fraction and at a liquid space velocity in the range from 0.25 to 6.0 volumes of said fraction per volume of catalyst per hour such that only a portion of said aromatic hydrocarbons is converted and the sulfur, naphthenic acids, and nitrogen content of said fraction is substantially reduced, the paraffins and naphthenes in said fraction being substantially unconverted removing said contacted fraction from contact with the catalyst, and recovering from said contacted fraction a lubricating oil of improved quality.

3. A method for treating a naphthenic lubricating oil fraction containing aromatic hydrocarbons and sulfur, naphthenic acids, and nitrogen which comprises contacting said fraction with a cobalt molybdate on silica-free alumina catalyst at a temperature in the range from 650 to 750 F., at a pressure in the range from 500 to 800 pounds per square inch gauge in the presence of hydrogen in an amount in the range from 200 to 2000 standard cubic feet per barrel of said fraction with a hydrogen consumption in the range from about 50 to about 400 standard cubic feet per barrel of said fraction and at a liquid space velocity in the range from 0.25 to 6.0 volumes of said fraction per volume of catalyst per hour such that only a portion of said aromatic hydrocarbons is converted and the sulfur, naphthenic acids, and nitrogen content of said fraction is substantially reduced, the paraffins and naphthenes in said fraction being substantially uncon= vetted removing said contacted fraction from contact with the catalyst, stripping said contacted fraction to remove therefrom products having a boiling range below that of the lubricating oil fraction, and recovering the stripped fraction.

4. A method in accordance with claim 3 in which the contacted fraction is stripped at a subatmospheric pressure with steam.

5. A method for treating a naphthenic lubricating oil raction containing aromatic hydrocarbons and sulfur, naphthenic acids, and nitrogen which comprises contacting said fraction with a catalyst consisting of an amount of cobalt molybdate in the range between 5% and 25% by weight and an amount in the range between 95% and by Weight of silica-free aluminumv at a temperature in the range from 650 to 750 F., at a pressure in the range from 500 to 800 pounds per square inch gauge in the presence of hydrogen in an amount in the range from 200 to 2000 standard cubic feet per barrel of said fraction with a hydrogen consumption in the range from about 50 to about 400 standard cubic feet per barrel of said fraction, and at a liquid space velocity in the range from 0.25 to 6.0 volumes of said fraction per volume of catalyst per hour such that only a portion of said aromatic hydrocarbons is converted and the sulfur, naphthentic acids, and nitrogen content of said fraction is substantially reduced, the paraflins and naphthenes in said fraction being substantially unconverted removing said contacted fraction from contact with the catalyst, stripping said contacted fraction to remove therefrom products having a boiling range below that of the lubricating oil fraction and recovering the stripped fraction.

6. A method in accordance with claim 5 in which the catalyst consists of 15% by weight cobalt molybdate and by weight of silica-free alumina.

References Cited in the file of this patent UNITED STATES PATENTS 1,933,047 Clark Oct. 31, 1933 1,944,236 Haslam Jan. 23, 1934 1,955,861 Russell et al Apr. 24, 1934 2,325,034 Byrns July 27, 1943 2,487,466 Nahin Nov. 8, 1949 

1. A METHOD FOR TREATING A NAPHTHENIC LUBRICATING OIL FRACTION CONTAINING AROMATIC HYDROCARBONS AND SULFUR, NAPTHENIC ACIDS, AND NITROGEN WHICH COMPRISES CONTACTING SAID FRACTION WITH A COBALT MOLYBDATE ON SILCA-FREE ALUMINA CATALYST AT A TEMPERATURE IN THE RANGE FROM 650* TO 750*F., AT A PRESSURE IN THE RANGE FROM 500 TO 800 POUNDS PER SQUARE INCH GUAGE IN THE PRESENCE OF HYDROGEN IN AN AMOUNT IN THE RANGE FROM 200 TO 2000 STANDARD CUBIC FEET PER BARREL OF SAID FRACTION WITH A HYDROGEN CONSUMPTION IN THE RANGE FROM ABOUT 50 TO ABOUT 400 STANDARD CUBIC FEET PER BARREL OF SAID FRACTION, AND AT A LIQUID SPACE VELOCITY IN THE RANGE FROM 0.25 TO 6.0 VOLUMES OF SAID FRACTION PER VOLUME OF CATALYST PER HOUR SUCH THAT ONLY A PORTION OF SAID AROMATIC HYDROCARBONS IS CONVERTED AND THE SULFUR, NAPTHENIC ACIDS, AND NITROGEN CONTENT OF SAID FRACTION IS SUBSTANTIALLY REDUCED, THE PARAFFINS AND NAPHTHENES IN SAID FRACTION BEING SUBSTANTIALLY UNCONVERTED. 